If it's an ambient generic adjust the "Max Audible Distance"

The "play everywhere" flag is set on all of them; will the radius still impact the sound?

No it won't. When you say you are increasing the amplitude of the sound are you doing it using an external program?

Yeah, I just go into audacity and increase it like 200%, then save it into my gmod sounds folder and the addon folder (both under waluigi_pinball)

I subscribed to the map and just checked it out ingame. I am assuming you are using an ambient generic for the music that plays everywhere. Maybe that is overpowering all the other sounds to make them seem quiet? Not too sure just an idea, you could always use a env_soundscape for the music and ambient generics for all the other sounds. But I've never really had experience in this case, cause I've never used ambient generic that has the play everywhere flag on.

Maybe try to first disable the play everwhere ambient generic compile and see if the volume of your other ones have changed at all that would be the first step imo.

That's a good idea, but there's actually another sound effect that plays normally (with no amplitude augmentation, I might add); the launcher at the start comes in clear as a whistle, it's only the other sounds that seem to be an issue.

When you amplified the sounds that are too quiet did you even notice a change in the volume?

Yeah, they about exploded my headphones